Congenital and acquired cases of defective platelet function

• Congenital

  • Bernard-Soulier syndrome

    • AR deficiency of a platelet membrane glycoprotein that’s required for vWF-mediated platelet adhesion to collagen (the membrane protein is Ib-IX)

    • Associated with the presence of “giant” platelets and a mild thrombocytopenia with a disproportionate bleeding tendency

  • Glanzmann’s thrombasthenia

    • AR deficiency of membrane glycoprotein IIb-IIIa, which is required for platelet aggregation by binding to fibrinogen

    • There may e a severe bleeding tendency

  • Storage pool diseases

    • Normal initial aggregation with collagen or ADP cannot be maintained due to abnormalities of the release reaction

    • Platelet dense granules have decreased levels of ADP, ATP, prostaglandins, and serotonin

    • Examples: Hermansky-Pudlak, Chediak-Higashi, thrombocytopenia with absent radii (TAR syndrome), and Wiskott-Aldrich

  • Grey platelet syndrome

    • Alpha granules are deficient (a-SPD)

    • Variable thrombocytopenia and platelets look gray

• Acquired

  • Aspirin and other NSAIDS

    • Inhibit COX and thus synthesis of the platelet prostaglandins prostacyclin and thromboxane, which are involved with platelet aggregation and the subsequent release reaction

    • It’s a permanent inhibition, so bleeding time may be prolonged for up to 2 weeks post ingestion

    • Platelet dysfunction may be reversed with a transfusion of small numbers of platelets or with DDAVP

  • Uremia

    • Not really well understood why this causes problems

    • This may also be treated with DDAVP, but correction of underlying kidney d/o is very important

  • Acquired storage pool defect – seen in chronic liver disease

Category: Medical Subject Notes , Pathology Notes